JPS59217028A - Vibration isolating device for structure - Google Patents

Abstract

PURPOSE:To securely prevent a structure from vibrating at all times by supporting a weight pendulum through rolling elements on the supporting tables of a structure, and making the frequency of vibration of the normal mode of said weight pendulum constant errespective of its amplitude and setting it equal to the frequency of vibration of the normal mode of said structure. CONSTITUTION:A vibration isolating device 2 provided on the top of a jacket 1 on the sea level consists of supporting tables 4 in an oil tank 3, a weight pendulum 6 vibratively supporting on the supporting tables 4 through rollers 5, and a damping board 7 provided in the oil tank 3 and being immersed in the oil O. Since the roller receiving faces 10, 11 of said supporting table 4 and said weight pendulum 6 are curved in a cylcloidal curve form in the directionin which the roller 5 rolls, the frequency of vibration of the normal mode of the weight pendulum is made constant irrespective of its amplitude. And, the maximum radius of curvature of the cycloidal curve and the diameter of the roller 5 are determined so that the frequency of vibration of the normal mode of the weight pendulum is almost equal to that of the jacket 1 and, thereby, the resonance of the jacket 1 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vibration isolating device for structures, which reliably suppresses vibrations of structures without requiring any particular power and without depending on the amplitude of vibrations applied to the structure. The present invention relates to a vibration isolating device for structures that can prevent vibrations.

Conventionally, marine structures such as Noyaketsu and high-rise structures have adopted various earthquake-resistant structures that can withstand seismic forces. However, with this method of resisting or absorbing seismic force by the structure itself, the structure tends to be complicated or special, leading to an increase in construction cost and construction period.

The present invention has been developed in view of the above conventional problems, and an object of the present invention is to prevent the vibration of a structure without requiring power and regardless of the magnitude of the vibration amplitude of the structure. The object of the present invention is to provide a vibration isolating device with a simple structure.

A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

In Figure 1, 1 is a jacket installed on the seabed, and the top of the jacket 1 above the sea surface is
A vibration isolating device 2 is provided to prevent vibrations.

As shown in FIGS. 2 to 4, the vibration isolator 2 includes an oil tank 3 provided on the top of the jacket 1, a support stand 4 installed on the top of the jacket 1 inside the oil tank 3, and a support stand 4 on the support stand 4. A gravity pendulum 6 is supported through rollers 5 so that it can freely vibrate, and a damping plate 7 is provided by being immersed in the oil stored in the oil tank 3 and extending downward from the bottom surface of the gravity pendulum 6. It is mainly composed of 扛.

The vibration direction 8 of the gravity pendulum 2 is the left-right direction in FIGS. 2 and 3, and the vibration direction 8 is made to coincide with the vibration direction 9 of the jacket 1 to be vibration-proofed (see FIG. 1). It will be installed. The rollers 5 are hung between support stands 4°4 provided at appropriate intervals in the width direction of the oil tank 3, and are oriented in the vibration direction 8.
It is placed at right angles to the. Further, the damping plate 1 is also arranged perpendicularly to the vibration direction 8 of the gravity pendulum 6 in order to damp the vibration of the gravity pendulum 6. Also, the roller bearing surface 10 of the support base 4 that supports the rollers 5 and the roller bearing surface 11 of the roller bearing portion 6a of the gravity pendulum 6 are designed to enclose the rollers 5, as shown in an enlarged view in FIG. The roller bearing is curved to form the surface 1.
Contour lines i, o, a of the cross section in the imaging direction 8 of 0 and 11
, i 1a is formed into a cycloidal curve and b.

Next, the operation of this embodiment will be described.

The surfaces io and ii of the support base 4 and the roller holder part 6a which are inscribed with the roller 5 are curved to form a cycloid curve in the direction in which the roller 5 moves (vibration direction 8). The natural frequency of the gravity pendulum 6 is always a constant value expressed by the following equation, regardless of the magnitude of the amplitude of the gravity pendulum 6 due to the magnitude of the excitation force applied to the vibration isolator 2.

Here, f is the natural frequency of the gravity pendulum 6, g is the gravitational acceleration, R is the maximum radius of curvature of the cycloid curve, and d is the diameter of the roller 5. That is, the gravity pendulum 6 oscillates with complete isochronism.

On the other hand, the jacket 1 vibrates in response to seismic force, wave force, or wind power, and the jacket 1 resonates due to a component of the vibration that matches the natural frequency of the jacket 1 when an earthquake occurs.

Therefore, if the maximum radius of curvature R of the cycloid curve and the diameter d of the rollers 5 are set so that the natural frequency of the gravity pendulum 6 expressed by the above equation is equal to the natural frequency of the jacket 1, then the jacket 1 resonance can be prevented. That is, by doing this, when the jacket 1 resonates due to the excitation force of its natural frequency, the gravity pendulum 6 also resonates at the same frequency, and the vibrations of the gravity pendulum 6 cancel out the vibrations of the jacket 1. As a result, the vibration of the jacket 1 is suppressed and fL is suppressed. Furthermore, as mentioned above, the natural frequency of the gravity pendulum 6 is constant and isochronous regardless of its amplitude, so that vibrations can always be reliably damped regardless of the magnitude of the excitation force applied to the jacket 1. I can do it. (In Figure 5, 1
The dotted @ line indicates when the amplitude of the gravity pendulum 6 is medium, and the two-dot chain line indicates when the amplitude is large. ) Furthermore, the damping plate I and the rollers 5 attached to the gravity pendulum 6 are immersed in the oil O.
So, along with the photographing of gravity pendulum 6, the gravity pendulum 6 was
The damping force that brakes the motor moves. The damping force by the damping plate 7 can be adjusted by controlling the liquid level of the oil O in the oil tank 3 so that the vibration absorption effect of the vibration isolator 2 is enhanced. Note that, according to the theory of dynamic vibration absorbers, it is preferable that the specific vibration number of the gravity pendulum 6 of the vibration isolator 2 is slightly smaller than that of the jacket 1.

FIG. 6 is a graph showing calculation results of the vibration characteristics of vibrations occurring in a structure when the vibration isolating device 2 is provided and when the structure is not provided.

In the figure, A is when this vibration isolator is not installed, and B
is what it was when it was set up. As shown in the figure, by providing this device, the vibration amplitude of the structure is reduced to less than half compared to when it is not provided. In addition, this calculation result shows that the vibration weight of the structure is 5000 TON (-m+g), the weight of the gravity pendulum is 250 TON (=mzg), and the roller bearing has a surface i.
The maximum radius of curvature of the cycloid o and ii is 400 mm, the diameter of the roller 5 is 300 mm, and the ratio V2/ of the natural frequency νl of the gravity pendulum 6 to the natural frequency ν2 of the structure is 0.95.
, the structure, and the damping ratio of the gravitational pendulum are set to 0.05. Note that the subscript 1 above represents a structure, and 2 represents a gravitational pendulum.

In the above embodiment, a vibration isolator was installed at the top of the jacket 1 on the assumption that the top of the jacket 1 would vibrate in a vibration mode that becomes the antinode of vibration, but the vibration isolating device was installed at the top of the jacket 1. For structures that vibrate in a vibration mode that is an antinode, this vibration isolator is installed in the center of the structure. In addition, in the above embodiment, vibrations of the jacket 1 in one direction (left-right direction in FIG. 1) are prevented, but vibrations in the direction perpendicular to the jacket (front-back direction in FIG. 1) are prevented. , the same vibration isolator as the above-mentioned structure in which one pendulum vibrates in the front-rear direction is installed. In this case, when the natural frequency of the jacket 1 in the front-rear direction is different from that in the left-right direction, the shape of the sago-cloid curve is determined in accordance with the natural frequency of the jacket 1 in the front-rear direction. Further, in the above embodiment, an example was shown in which the rollers 5 were used as the rolling elements, but in addition to using a sphere instead of the rollers 5, the support for receiving the sphere and the support of the gravity pendulum rotate the surface of a cycloid curve. It may be configured to have a cup shape with a curved surface so that the gravity pendulum can vibrate in any horizontal direction. Furthermore,
In the above embodiment, the jacket 1 is provided with a vibration isolator, but it can of course be applied to land structures such as high-rise buildings.

In summary, according to the present invention, the following excellent effects can be obtained.

(1) Vibration of structures can be prevented without power.

(2) The natural frequency of the gravitational pendulum is constant regardless of its amplitude and is set almost equal to the natural frequency of the structure, so the vibration of the structure is always reliably maintained regardless of the amplitude of the structure's vibration. can be prevented.

(3) It has a very simple structure, can be applied to a wide range of structures, and is extremely useful.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment in which a jacket is provided with a vibration isolator according to the present invention, FIG. 2 is an enlarged front cross-sectional view of the vibration isolator, and FIG. 3 is a view of the vibration isolator shown in FIG. 4 is a sectional view taken along the line IV-IV in FIG. 2, FIG. 5 is an enlarged front view of a portion of the support shown in FIG. 2, and FIG. It is a graph showing the vibration characteristics (calculated values) of the structure when the device is installed and when the device is not installed. In the figure, 1 is a jacket, 2 is a vibration isolator, 4 is a support stand, and 5
6 is the gravity pendulum, 1 is the damping plate, 8 is the vibration direction of the gravity pendulum, 10 is the surface of the support base, 10a is its outline, 11 is the surface of the roller support of the gravity pendulum, 11a
is its outline and 0 is the oil. Patent applicant: Ishikawajima-Harima Heavy Industries Co., Ltd. Agent Patent attorney: Nobuo Kinutani

Claims (1)

[Claims] A support stand provided on the structure, a gravity pendulum supported on the support stand via rolling elements so as to be able to vibrate freely, and I'1. provided on the gravity pendulum. The natural frequency of the claw force pendulum is as above, and A vibration isolator for a structure, characterized in that it is formed in a cycloidal curve shape that is approximately equal to the natural frequency of the structure.